Progressive surface hardening and tempering of metal



Aug. 14, 1945. 5. SMITH 2,382,515

PROGRESSIVE SURFACE HARDENING- AND TEMPERING OF METAL Filed June 29, 1943 11 f 3%! GE m /0 1 MT INVENTOR. JTEPHEN JMITH BY a), 40

ATTORNEYS Patented Aug. 14, 1945 PROGRESSIVE SURFACE HARDENING AND TEMPERING OF METAL Stephen Smith, Jersey City,

N. J., asslgnor to Air Reduction Company, Incorporated Application June 29, 1943, Serial No. 492,701

8 Claims.

This invention relates .to progressive heat treatment of ferrous metal work-pieces to harden and temper their surface.

Mycopending application, Serial No. 438,237, filed April 9, 1942, discloses a method and apparatus for hardening and tempering the surface of metal work-pieces by moving a gas heating torch progressively along the work-piece closely followed by quenching jets. The quenching jets are followed by a reheating flame system to temper the surface to the desired hardness.

According to the present invention the surface of the work-piece is hardened to its fullest extent, as in the copending application, by moving a torch or other heating device progressively along the work-piece, or moving the work-piece progressively under the heating device, and immediately projecting quenching jets on the surface but the use of reheating flames to produce the tempering action is eliminated. Instead, the cooling effect of the quench is controlled so that a certain amount of residual heatis left in the mass of metal which will produce the desired tempering action when it is conducted to the hardened and quenched surface. To accomplish this the quenching medium is removed from the surface under treatment, preferably by the use of air jets, while there is still a sufficient amount of heat in the metal below the quenched surface to produce the desired tempering effect when it is conducted back to the surface. The time that the quenching medium remains on the hardened surface is regulable to produce the particular tempering action desired. The regulation is preferably obtained by adjusting the distance from the quenching jets to the place at which the air jets strike the surface of the work-piece, or by altering the pressure of the air jets. The invention comprehends not only a method of hardening and tempering in this manner, but also improved apparatus suitable for use in carrying out the method.

In the accompanying drawing:

Figure 1 is a more or less diagrammatic representation in side elevation of one form of apparatus embodying the invention and which is capable of carrying out the improved method;

Fig. 2 is a front elevation of the lower portion of the apparatus shown in Fig; 1 as viewed from the left in that figure;

Fig. 3 is a horizontal section taken on the line 3-3 of Fig. 1; and

Fig. 4 is a. view similar to the lower portion of Fig. 1, illustrating a modification of the invention.

Referring first to Figs. 1 to 3 the apparatus therein illustrated comprises a heating torch having a tip I of the block type. The torch tip has orifices from which high intensity heating fiames 2, such as oxyacetylene flames, are directed against the surface of /a work-piece W. There are preferably several rows of such orifices extending across the width of the surface to be hardened, two rows being shown in Fig. 1. The torch tip has an additional row of orifices, likewise extending across the width of the surface under treatment, from which quenching jets 3 are directed against the work surface. The quenching medium may be water or any other suitable cooling liquid, and may be supplied to the quenching jet orifices from a distributing chamber 4 within the torch tip.-

A blast pipe 5 positioned at the rear of the torch and extending transversely across the surface under treatment is provided with a row of orifices 6 (Fig. 2) adapted to direct air or gas jets I (Fig. 1) forwardly against the work surface a predetermined distance behind the quenching jets 3. The blast pipe 5 is supported in any suitable way so that the distance behind the quenching jets 3 at which the air jets I strike the work surface may be regulated. One way of accomplishing this is to attach brackets 8 and 9 to the ends of the torch tip. as shown in Fig. 3. Each of the brackets has a rearward extension I0 provided with an elongated horizontal slot Ilia. A pair of arms II are pivoted to the extensions It by means of a bolt l2 which passes through the slots Illa. These arms extend downwardly and rearwardly toward the surface of the workpiece. The blast pipe 5 is swivelly supported between the lower ends of the arms H so that it may be turned about its longitudinal axis to vary the angle at which the air jets 1 are projected against the work surface. Air may be supplied to the blast pipe 5 under pressure by means of a conduit [3 (Figs. 2 and 3).

Relative movement between the work-piece and the parts of the apparatus above described to effect the progressive treatment may be produced by moving the work-piece under the apparatus or by moving the apparatus progressively along the work-piece. In the latter case the parts already described may be supported from a self-propelled carriage [4 (Fig. 1). This carriage, shown on a reduced scale, has wheels I5 run on a track IS. The front wheels are driven by an electric motor l'lprovided with an adjustable centrifugal speed governor IS. The governor may be adjusted by means of a knob ends of the extensions It on the 'torch brackets I and 9. i

As the self-propelled carriage moves the heating torch and its associated parts along the surface of the work piece, the flame Jets 2 heat the metal of the work-piece above its critical temper-.

atures. The hot surface is immediately quenched by the quenchin lists 3. The quenching medium issues from the quenching orifices in the torch tip in suitable volume and at proper pressure to cool the work surface at a rate which will harden it to the fullest extent. The blast pipe 6 is so adjusted about its longitudinal axis that the air jets I issuing from it are directed forwardly and at such an angle to the surface of the work-piece that the quenching liquid is substantially removed by them from the surface under treatment. The distance from the quenching jets to the air jets determines the length of time the quenching liquid remains on the surface of-the work-piece and therefore the amount of heat remaining in the work-piece after quenching. This distance may be adjusted by turning the blast pipe about its longitudinal axis, by swinging the arms H about the axis of the bolt I2, by shifting the bolt i2 in the slots Illa laterally of itself and longitudinally of the slots, or by changing the air pressure, or by any combination of these things. The residual heat in the mass of metal below the quenched surface is conducted to the hardened surface and is utilized to temper it. The extent of the tempering action depends upon how long the quenching medium is allowed to remain on the surface of the work-piece and hence the amount of tempering heat that remains in the metal after quenching. If the parts are adjusted so that the air jets strike the surface of the work-piece a relatively short distance behind the quenching jets then the quenching medium is permitted to remain on the surface of the work-piece only a relatively short time and a relatively large amount of tempering heat will remain in the metal, and the tempering action will therefore be relatively great. 0n the other hand, if the parts'are adjusted so that the air Jets strike the surface of the work-piece a greater distance behind the quenching lets the quenching medium will remain on the surface of the work-piece a greater length of time, and less tempering heat will remain'in the metal and the tempering action will therefore be less.

In the modification of Fig. 4 the torch tip 24 is of slightly different construction from the torch tip i. There are two rows of jet orifices from which flame jets 2 are directed against the surface of the work-piece but in place of the row of rearwardly directed orifices from which the quenching jets 3 are directed in Fig. 1, the torch tip 24 of Fig. 4 has a distributing chamber .25

communicating with several rows of orifices directed substantially straight downward through the bottom face of the torch tip. Streams 2B of quenching liquid flow under low pressure or by gravity from the distributing chamber 25 through the orifices into contact with the surface of the work-piece. There is a ridge 21 between the heating flames 2 and the quenching streams 26 for shielding the flame jets and the quenching streams from each other.

To effect greater control of the removal of quenching liquid from the surface of the workpiece a baffle plate 28 may be employed supported in any suitable way. For instance, it may be connected to the torch tip 24 by a bolt 29 and held at a spaced distance behind the quenching streams by means of a spacer 30 surrounding the bolt. The baflle extends close to the surface of the work-piece and permits only a minimum quantity of quenching medium to pass under it. This makes it possible to reduce the pressure of the air 'Jets 1 since they need not be directed against the surface of the work-piece with so much force when the major portion of the quenching medium has been removed by the baffle 2!. The baffle also minimizes the amount of splashing that occurs when the compressed air Jets strike the quenching stream.

The apparatus shown in Fig. 4 also has forward extensions H! on the brackets 8 and 8 which support arms 3i similar to the arms H. The arms 3| adjustably support a pipe 32 in the same manner that the arms it support the blast pipe 5. The lower portion of the pipe 32 is provided with one or more rows of orifices from which precooling jets '33 of water, or the like, are directed against the surface of the 'workpiece in advance of the heating torch. The Jets extend across the full width of the surface under treatment and produce a stream of cooling liquid of suflicient volume to cool the mass of metal to uniform-temperature prior to heating the surface by means of the torch 24. This insures against any preheating which would gradually increase the temperature of the mass as the operation progresses over a work-piece of considerable length.

If desired, the baffle or the precooling means shown in Fig. 4, or both, may be used in the form of the apparatus illustrated in Fig. l.

The heating of the metal above its critical temperature prior to quenching may be accomplished by means other than the gas torch shown in Figs. 1 and 4. For instance, it could "be done by means of a heater of the electric induction type.

While the invention is intended for heat treating ferrous metal, such as steel, it may be employed in the treatment of any work-piece made of metal that can be hardened and tempered by heating above a critical temperature and then quenching and reheating it.

I claim:

1. The method of hardening and tempering the surface of a ferrous metal work-piece hardenable by heating and quenching which comprises progressively applying heat to the work surface to heat the metal above its critical temperature, progressively applying a quenching liquid to the heated work surface, and at a predetermined distance behind the place of application of the quenching liquid removing the quenching liquid from the surface under treatment, said distance being such that the quenching liquid leaves in the mass of metal an amount of residual heat which when conducted to the hardened surface will temper it to the desired extent in the absence of any other reheating of such hardened surface.

2. The method of hardening and tempering the surface of a ferrous metal work-piece hardenable by heating and. quenching which comprises pro- 76 'gressively applying heat to the work surface to heat the metal above its critical temperature, progressively applying a quenching liquid to the heated work surface close behind the place of heat application, and at a predetermined distance behind the place of application of the quenching liquid directing an air blast against the work surface to remove the quenching liquid from the surface under treatment, said distance being such that the quenching liquid leaves in the mass of metal an amount of residual heat which when conducted to the hardened surface will temper it to the desired extent in the absence of any other reheating of such hardened surface.

3. The method of hardening and tempering the surface of a ferrous metal workpiece hardenable by heating and quenching which comprises progressively applying heat to the work surface to heat the metal above its critical temperature, progressively applying a quenching liquid to the heated work surface to harden the surface metal to the fullest extent, and tempering the hardened surface metal to a predetermined extent by removing the quenching 'liquid' from the surface under treatment at a place to the rear of the place of application of the quenching liquid, and adjusting the distance between the places of application and removal of the quenching liquid such that an amount of residual heat will be left in the mass of metal which when conducted to the hardened surface will temper it to said predetermined extent in the absence of any other reheating of such hardened surface.

4. The method of hardening and tempering the surface of a ferrous metal work-piece hardenable by heating and quenching which comprises progressively precooling the work surface, progressively applying heat to the work surface behind the place of precooling to heat the metalaibove its critical temperature, progressively applying a quenching liquid to the heated work surface, and at a predetermined distance behind the place of application of the quenching liquid rework surface at which the quenching liquidis applied and removed, whereby the length of time during which the quenching liquid is effective may be varied.

6. Apparatus for hardening and tempering the surface of a ferrous metal work-piece hardenable by heating and quenching comprising a common support, heating means carried by said support for heating the work surface above its critical temperature, means carried by said support for applying a quenching liquid to the heated work surface, means carried by said support behind said last-named means for removing the quenching liquid from the surface under treatment before said surface is fully quenched,

, means for producing relative movement of the work-piece and said common support, and means for adjusting the quenching liquid removing means on said support to vary the distance between the places on the work surface at which the quenching liquid is applied and removed,

whereby the-length of time during which the quenching liquid is effective may be varied.

7. Apparatus for hardening and tempering the surface of a. ferrous metal work-piece hardenable by heating and quenching comprising a torch for heating the work surface above its critical temperature, means for applying a quenching liquid to the heated work surface, means behind the last-named means for removing the quenching liquid from the surface under treatment before said surface is fully quenched, a common support for the torch and the means for applying and removing the quenching liquid,

means for roducing relative movement of the moving the quenching liquid from the surface under treatment, said) distance being such that the quenching liquid leaves in the mass of metal an amount of residual heat which when conducted to the hardened surface will temper it to the desired extent in the absence of any other reheating of such hardened surface. v

5. Apparatus for hardening and tempering the surface of a ferrous metal work-piece'hardento be hardened and tempered, and means for adjusting the quenching liquid removing means on said common support to vary the distance between the places on the work surface at which the quenching liquid is applied and .removed whereby the length of time during which the quenching liquid is effective may be varied.

8. Apparatus for hardening and tampering the surface of a ferrous metal work-piece hardenable by heating and quenching comprising a common a blastpipe carried by said support behind said last-named means for directing a stream of air against the work surface to remove the quenching liquid from the. surface under treatment before said surface is fully quenched, means for producing relative movement of the work-piece and under treatment before said surface is fully.

quenched, means for producing relative movement of the work-piece on the one hand and all of said means on the other hand, andmea'ns for adjusting the quenching liquid removing means said common support, and means for adjusting said blast pipe to vary the distance betweenthe places on the work surface at which the quenching liquid is applied and removed, whereby the length of time during which the quenching liquid is effective may be varied.

"- S'IEPHEN SMITH. 

